The research objectives of this proposal include a study of the interactions between coagulation factors and vascular endothelial cells, with specific interest in mechanisms by which activation of coagulation may be regulated by endothelium. I have obtained preliminary information demonstrating that intact vascular endothelial cells, but not vascular smooth muscle cells, fibroblasts or corneal endothelial cells, inhibit blood coagulation. Having obtained these data and additional information that this inhibition occurs at the initial stage of activation of coagulation (contact pathway), I propose 1) to determine how vascular endothelial cells inhibit clotting by characterizing the component(s) in intact cells responsible for inhibition and identifying the coagulatino reaction(s) inhibited; 2) to characterize the binding of purified Factor Xa to specific sites on vascular endothelium; and 3) to determine the effects of other cells, such as fibroblasts and vascular smooth muscle cells as well as the extracellular matrix from endothelial cells, on blood coagulation and the mechanisms responsible for these effects. The methods to be used for this research will include purification of coagulation factors, X, XI and XII; establishment of endothelial cells as well as vascular smooth muscle cells in tissue culture, and production of extracellular matrix. Additionally, vascular cell components, including glycosaminoglycans, will be purified in order to study their effects on coagulation. Long-term research objectives also include using this experimental model to determine whether coagulation is modified after endothelial cell injury by pathologic stimuli, such as high concentrations of low density lipoproteins, neutrophil degranulation, or mechanical injury. These studies may identify previously unrecognized normal and pathological interactions between vascular cells and the coagulation system. Moreover, they may provide information which would enhance our understanding of the role of coagulation in atherogenesis.